Ablation device for reducing damage to vessels and/or in-vivo stents

ABSTRACT

An ablation burr has a body provided with an inner circumferential rim and an outer circumferential rim that are concentric and spaced longitudinally by a selected distance along the length of the burr. The outer circumferential rim has a generally smooth convex outer surface that reduces damage to a vessel wall or stent. A leading surface of the burr extends between the inner and outer circumferential rims in a substantially uniform, concave manner. An abrasive, for example, diamond grit, is provided on the leading surface. The burr is selectively rotated by a drive shaft, causing the abrasive leading surface of the burr to ablate unwanted deposits. If desired, a wire extends co-axially through the body such that a distal end of the wire extends out of the distal end of the burr. An abrasive tip may be coupled to the distal end of the wire, and is selectively rotated, to ablate unwanted deposits. The burr may be made of a compressible elastomeric material, to facilitate positioning the burr through restrictive openings, such as the coronary ostia. To prevent the burr from becoming welded to a spring tip at the end of the guide wire, a bearing may be provided at a distal region of the guide wire. The bearing has a dynamic member that acts as a bumper and rotates when the ablation device is advanced to the distal region of the guide wire and contacts the dynamic member. In an alternative embodiment of the invention, the leading surface of the burr includes one or more aspiration ports through which debris that is ablated from the occlusion may be removed from a patient&#39;s vessel.

CROSS REFERENCE TO APPLICATIONS

The present invention is a continuation-in-part of U.S. patentapplication Ser. No. 09/035,734, filed Mar. 5, 1998, now U.S. Pat. No.6,015,420 which is a continuation in part of U.S. patent applicationSer. No. 08/813,827 and U.S. patent application Ser. No. 08/812,715,both filed on Mar. 6, 1997 both abandoned.

FIELD OF THE INVENTION

The present invention generally relates to devices for removingundesirable deposits from the lumen of a blood vessel or of a stentpositioned in a blood vessel, and more particularly, to atherectomydevices.

BACKGROUND OF THE INVENTION

Vascular diseases, such as atherosclerosis and the like, have becomequite prevalent in the modern day. These diseases may manifestthemselves in a number of ways, often requiring different forms ormethods of treatment for curing the adverse effects of the diseases.Vascular diseases, for example, may take the form of deposits or growthsin a patient's vasculature which may restrict, in the case of a partialocclusion, or, stop, in the case of a total occlusion, blood flow to acertain portion of the patient's body. This can be particularly seriousif, for example, such an occlusion occurs in a portion of thevasculature that supplies vital organs with blood or other necessaryfluids.

To treat these diseases, a number of different therapies have beendeveloped. While a number of effective invasive therapies are available,it is desired to develop non-invasive therapies as well. Non-invasivetherapies may be more desirable because of the possibility of decreasedchances of infection, reduced post-operative pain, and lesspost-operative rehabilitation. Drug therapy is one type of non-invasivetherapy developed for treating vascular diseases. Clot-dissolving drugshave been employed to help break up blood clots which may be blocking aparticular vascular lumen. Other drug therapies are also available.Further, non-invasive intravascular treatments exist that are not onlypharmaceutical, but also physically revascularize lumens. Two examplesof such intravascular therapies are balloon angioplasty and atherectomy,both of which physically revascularize a portion of a patient'svasculature.

Balloon angioplasty is a procedure wherein a balloon catheter isinserted intravascularly into a patient through a relatively smallpuncture, which may be located proximate the groin, and intravascularlynavigated by a treating physician to the occluded vascular site. Theballoon catheter includes a balloon or dilating member which is placedadjacent the vascular occlusion and is then inflated. Intravascularinflation of the dilating member by sufficient pressures, on the orderof 5 to 12 atmospheres or so, causes the balloon to displace theoccluding matter to revascularize the occluded lumen and thereby restoresubstantially normal blood flow through the revascularized portion ofthe vasculature. It should be recognized that this procedure does notremove the matter from the patient's vasculature, but displaces andreforms it.

While balloon angioplasty is quite successful in substantiallyrevascularizing many vascular lumens by reforming the occludingmaterial, other occlusions may be difficult to treat with angioplasty.Specifically, some intravascular occlusions may be composed of anirregular, loose or heavily calcified material which may extendrelatively far along a vessel or may extend adjacent a side branchingvessel, and thus may not be prone or susceptible to angioplastictreatment. Even if angioplasty is successful, there is a chance that theocclusion may recur. Recurrence of an occlusion may require repeated oralternative treatments given at the same intravascular site.

A relatively new technique to reduce the recurrence of occlusion after aballoon angioplasty procedure involves providing a stent at therevascularized site. A stent is typically a hollow tube, typicallybraided, that can be inserted into the vascular of a patient in acompressed form. Once properly positioned at a desired site, the stentis expanded to hold the vessel open in an attempt to prevent restenosis.While this technique can help maintain blood flow past the site, it hasbeen found that the occluding material often migrates through theinterstices of the stent braid, and may again occlude the vessel. Thisphenomenon is sometimes referred to as interstitial hyperplasia.

Accordingly, attempts have been made to develop other alternativemechanical methods of non-invasive, intravascular treatment in an effortto provide another way of revascularizing an occluded vessel and ofrestoring blood flow through the relevant vasculature. These alternativetreatments may have particular utility with certain vascular occlusions,or may provide added benefits to a patient when combined with balloonangioplasty, drug and/or stent therapies.

One such alternative mechanical treatment method involves removal, notdisplacement of the material occluding a vascular lumen. Such treatmentdevices, sometimes referred to as atherectomy devices, use a variety ofmaterial removal means, such as rotating cutters or ablaters forexample, to remove the occluding material. (The term “atherectomydevice” as used throughout the specification refers to ablation devicesfor use in any portion of a patient's vasculature. Thus, while theatherectomy devices provided in accordance with preferred embodiments ofthe present invention are well suited for use in the coronary arteries,their use is not limited to the coronary arteries.) The material removaldevice is typically rotated via a drive shaft that extends out of thevascular of the patient and to an electric motor.

In operation, an atherectomy device is typically advanced over a guidewire placed in vivo until the material removal device is positioned justproximal to the occluded site. The motor is used to rotate the driveshaft and the material removal device, and the material removal deviceis moved through the occluded vessel. The material removal deviceremoves the material from the vessel, rather than merely displacing orreforming the material as in a balloon angioplasty procedure.

A potentially negative characteristic for all atherectomy devices is theunwanted perforation of a vessel wall by the material removal device.This can occur when the material removal device improperly engages thevessel wall, for example when the material removal device is notoriented substantially parallel to the axis of the vessel. In thissituation, the material removal device (e.g., cutter or abrasiveablater) may improperly engage the vessel wall and cause unwanted damagethereto.

Similarly, an atherectomy device may cause damage to an in vivo stentwhen used to remove occluding material from within the stent caused by,for example, interstitial hyperplasia. Even a properly oriented materialremoval device may damage a stent. If the cutter or ablater of a typicalatherectomy device engages a stent, particulates of the stent and/ormaterial removal device may be removed and introduced into thevasculature of the patient, which can cause complications. To reducethis risk, the material removal device typically has an outer diameterthat is substantially less than the inner diameter of the stent. It isbelieved that this may reduce the risk that the material removal devicewill engage and thus damage, the stent. A limitation of this approach isthat a substantial gap typically must be provided between the materialremoval device and the stent. This may reduce the amount of occludingmaterial that can be removed from within the stent. Accordingly, thestent will likely become occluded again sooner than if the outerdiameter of the material removal device could more closely match theinner diameter of the stent, and remove more of the occluding material.

Given the above-discussed considerations, it would be desirable toprovide an atherectomy device that can reduce the risk of damage to avessel wall and/or an in vivo stent. In particular, it would beadvantageous to provide an atherectomy device that can align the burrcutting action with a path through the stenosed vessel while removingunwanted material and yet not cause excessive wear on the vessel walls.The present invention fulfills these needs, and provides further relatedadvantages.

SUMMARY OF THE INVENTION

The present invention overcomes many of the disadvantages of the priorart by providing an atherectomy device that may reduce the risk ofdamage to a vessel wall and/or an in vivo stent. In one embodiment ofthe present invention, an atherectomy device is provided that has arotatable ablation burr attached to the distal end of a flexible driveshaft. The ablation burr can have generally elliptical proximal anddistal shoulders and a generally cylindrical material removal portiontherebetween. In a preferred embodiment, the material removal portion issubstantially cylindrical and is recessed relative to the shoulders. Ina preferred embodiment, the material removal portion contains abrasivematerial such as diamond grit adhered to the outer surface.

The proximal and distal shoulders are substantially less abrasive thanthe material removal portion. The shoulders are tapered and act to alignthe burr along a path through the stenosed vessel. Aligning the burrallows an unwanted, projecting deposit to be presented to the materialremoval portion while the less abrasive shoulders are presented to thevessel wall. The shoulders can serve to re-align the burr when the burrassumes a cant due to a tortuous path through a stenosed vessel.

In another embodiment of the present invention, an atherectomy device isprovided that has a flexible drive shaft with an ablation burr attachedto the distal end thereof. The ablation burr is preferably generallyelliptical in shape except for a concave shaped leading surface. Anabrasive grit is then disposed on the concave shaped leading surface.Extending distally from the concave shaped leading surface is a distaltip portion, and extending proximally from the concave shaped leadingsurface is a convex shaped portion. Both the distal tip portion and theconvex shaped portion have non-abrasive surfaces.

In this configuration, the abrasive grit is effectively prevented fromengaging a vessel wall regardless of the orientation of the ablationburr within the vessel. That is, the non-abrasive surfaces of the distaltip and the convex shaped portion will tend to engage the vessel wallbefore the concave shaped leading surface, and may effectively preventthe abrasive grit of the concave shaped leading surface from engagingthe vessel wall. To further reduce the friction between the ablationburr and the vessel wall, the convex shaped portion may have a number ofdimples formed therein.

It is recognized that the benefits of this embodiment may equally applywhen the ablation burr is used to remove unwanted deposits from within astent (e.g., interstitial hyperplasia). In this application, however,the present invention may effectively prevent the abrasive grit on theconcave shaped leading surface from engaging the stent, rather than theinterstitial hyperplasia. This may reduce the risk of damage to thestent.

In another embodiment of the present invention, the ablation burr mayinclude an outer surface which is generally non-abrasive, but has anumber of depressions therein forming a number of depressed surfaces. Anabrasive is provided only on the depressed surfaces. In thisconfiguration, all of the abrasive is positioned just below the outersurface of the ablation burr. Accordingly, only the non-abrasive outersurface of the ablation burr contacts the stent. The occluding materialwithin the stent, however, may enter the depressions and become ablated.Preferably, the depressions form a number of depressed flutes in theouter surface of the ablation burr.

In another embodiment of the present invention, the ablation burr has agenerally elliptical outer surface with a selected portion of the outersurface having an abrasive coating. The abrasive coating is formed froma material that is softer than the material used to form the stent.Accordingly, the abrasive may not damage the stent. In a preferredembodiment, the abrasive includes a number of chips or a grit thatcomprises plastic or some other malleable material that is softer thanthe material used to form the stent. It is known that stents aretypically formed from stainless steel or Nitinol.

In another embodiment of the present invention, the atherectomy deviceincludes a cutter device rather than an ablation device on distal endthereof. The cutter device may be generally elliptical in shape, and mayhave a number of cutter blades on at least a leading surface thereof. Inthis embodiment, at least a portion of selected cutter blades are madefrom a material that is softer than the material used to form the stent.As indicated above, stents are typically made from either stainlesssteel or Nitinol. In the present embodiment, it is contemplated that thecutter blades can be made from a softer material such as aluminum,titanium or annealed stainless steel. These materials are advantageousin that they are very ductile. It is contemplated, however, that thecutting blades may be surface hardened by oxidizing, nitriding,carbonizing or by some other process to maintain a sharp cutting edge. Asharp cutting edge is often important to minimize the particle size ofthe ablated atheroma. If the burr contacts the stent, the underlyingductile burr material preferably plastically deforms, thus preventingparticle generation from either the burr or the stent.

An advantage of all of these embodiments is that the material removaldevice (e.g., cutter or ablater) can have an outer diameter that moreclosely matches the inner diameter of a stent. In prior atherectomydevices, the material removal device typically had an outer diameterthat was substantially less than the inner diameter of the stent toreduce the risk that the material removal device will engage, and thusdamage, the stent. However, in the present invention, appropriateportions of the material removal devices are formed from a softermaterial than the stent. This may allow the material removal device toengage the stent without substantially damaging the stent. Accordingly,the present invention may allow the material removal device to have anouter diameter that more closely matches the inner diameter of thestent, which may allow the material removal to remove more of theoccluding matter from the stent.

In another preferred embodiment of the present invention, the ablationdevice includes a burr having an inner circumferential rim at the distalend of the burr and an outer circumferential rim that is spacedlongitudinally from the inner circumferential rim by a first distance.The outer circumferential rim defines a maximum diameter of the burr. Aleading surface extends between the inner and outer circumferential rimsin a substantially uniform, concave manner. An abrasive is provided onthe leading surface, and the burr is coupled to a drive shaft thatselectively rotates the burr. Furthermore, the outer circumferential rimis preferably non-abrasive and is convex in profile.

In another embodiment of the present invention, a wire extendsco-axially through the burr, such that a first distal end of the wireextends out of the body, distal to the first annular edge. An abrasivetip is coupled to a distal end of the wire and is selectively rotated toablate unwanted deposits.

In another embodiment of the present invention, the burr is made of acompressible, elastomeric material. The burr is positioned in acompressed condition within a guide catheter for positioning at adesired location within a patient's vasculature. Once the guide catheteris at the desired location, the burr is pushed out of the catheter,allowing it to expand to a operational expanded condition.

In another embodiment to the present invention, an ablation device isadvanced to a desired site within a patient's vasculature over a guidewire having a bearing provided at a distal region of the guide wire. Thebearing has a dynamic member that acts as a bumper and rotates when theablation device is advanced to the distal region of the guide wire andcontacts the dynamic member. The guide wire having the bearing isadvanced through the patient's vasculature until the bearing ispositioned just distal of the unwanted deposit or lesion.

In another embodiment of the invention, an atherectomy burr having arelatively flat leading surface includes one or more aspiration portsthrough which particles ablated from a patient's vessel may be removed.The burr is driven with a substantially sealed drive shaft that mayinclude a section of heat shrink tubing sandwiched between filarwindings. The proximal end of the sealed drive shaft is connected to aregular atherectomy drive shaft through a coupling. The couplingincludes a window that rotates with the burr. Surrounding theconventional drive shaft and coupling is a sheath. The proximal end ofthe sheath is connected to a source of vacuum that draws particlesaspirated from the patient through the front face of the burr, thesealed drive shaft and through the window of the coupling. The particlesthen are drawn along the lumen of the shaft to a filter that is in linewith the source of vacuum.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thisinvention will become more readily appreciated as the same becomesbetter understood by reference to the following detailed description,when taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a side elevational view of an atherectomy device in accordancewith a first embodiment of the present invention, including a concaveshaped leading surface;

FIG. 2 is a side elevational view of the embodiment shown in FIG. 1ablating an occluded vessel;

FIG. 3 is a side elevational view of the embodiment shown in FIG. 1ablating an occluded stent;

FIG. 4 is a side elevational view of an atherectomy device in accordancewith another embodiment of the present invention, including a number offluted depressions in the outer surface of the ablating burr;

FIG. 5 is a front view of the embodiment shown in FIG. 4;

FIG. 6 is a side perspective view of another embodiment of the presentinvention, including an abrasive outer surface that is formed from amaterial that is softer than the material used to form the stent;

FIG. 7 is a partial cross sectional view of another embodiment of thepresent invention including a number of cutter blades;

FIG. 8 is a cross-sectional side view taken along lines 8—8 of FIG. 7;

FIG. 9 is a side elevational view of the embodiment shown in FIG. 7cutting through an occluded stent;

FIG. 10 is a fragmentary, side, perspective view of an atherectomydevice having a guide wire disposed therethrough;

FIG. 11 is a fragmentary, side, perspective view of the atherectomydevice disposed within a lumen having an asymmetrical lesion;

FIG. 12 is a side elevational view of a currently preferred embodimentof the atherectomy device including a concave shaped leading surfaceaccording to the present invention;

FIG. 13 is an enlarged view of a portion of the atherectomy deviceillustrated in FIG. 12;

FIG. 14 is a side elevational view of an alternative embodiment of theatherectomy device according to the present invention;

FIG. 15 is a side elevational view of another alternative embodiment ofthe atherectomy device according to the present invention;

FIG. 16 is a side elevational view of another alternative embodiment ofthe atherectomy device according to the present invention, illustratingan ablative wire;

FIG. 17 is a front isometric view of another alternative embodiment ofthe atherectomy device according to the present invention;

FIG. 18 is a side elevational view of an expandable atherectomy devicehaving a concave leading surface according to another aspect of thepresent invention;

FIG. 19 is a side elevational view of the device illustrated in FIG. 18,in an expanded position;

FIG. 20 is a top plan view of a joining mechanism used in the expandableatherectomy device illustrated in FIGS. 18 and 19;

FIG. 21 is a side elevational view of a drive coil provided inaccordance with yet another aspect of the present invention;

FIG. 22 illustrates a guide wire having a bearing position at its distalend disposed within a lumen according to another aspect of the presentinvention;

FIG. 23 is an enlarged side elevational view of the bearing illustratedin FIG. 22; and

FIG. 24 illustrates an atherectomy burr including a number of aspirationports on its leading surface according to another aspect of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a side elevational view of an atherectomy device in accordancewith a first embodiment of the present invention. The atherectomy deviceis generally shown at 10, and includes a flexible drive shaft 12 and anablation burr 14. The flexible drive shaft 12 and ablation burr 14 havea lumen extending therethrough to receive a guide wire 16, as shown. Inoperation, the guide wire 16 is percutaneously inserted through thevasculature of a patient, and past the desired occlusion site. Theatherectomy device 10 is then slid over the guide wire 16 until theablation burr 14 is positioned just proximal to the occlusion site. Aguide catheter may be used to assist in the positioning of both theguide wire 16 and the atherectomy device 10, as is known in the art. Theproximal end of the drive shaft remains outside the body and is attachedto an electric motor. The motor rotates the atherectomy device while theatherectomy device is advanced distally through the occlusion site. Theablation burr 14 removes the occluding material by ablation.

Preferably, the atherectomy device 10 comprises a flexible drive shaft12 attached to an ablation burr 14, wherein the flexible drive shaft 12and the ablation burr 14 are disposed about a central axis 24. Theablation burr 14 has a first cross section 26 spaced from a second crosssection 28, wherein the second cross section 28 has a larger crosssectional area than the first cross section 26. The ablation burr 14further has a first outer surface 18 that extends between the firstcross section 26 and the second cross section 28, and extends inwardtoward the central axis 24 relative to an imaginary line 31 that extendsbetween the first cross section 26 and the second cross section 28 asshown.

The atherectomy device 10 may further have a third cross section 30spaced relative to the second cross section 28, wherein the ablationburr 14 includes a second outer surface 22 that extends between thesecond cross section 28 and the third cross section 30. The second outersurface 22 extends outward away from the central axis 24 relative to animaginary line 32 that extends between the second cross section 28 andthe third cross section 30.

More specifically, and in a preferred configuration, the ablation burr14 is generally elliptical in shape, except for a concave shaped leadingsurface 18 as shown. An abrasive grit 19, shown in a cross hatch, isdisposed on the concave shaped leading, surface 18. The abrasive gritmay be a diamond grit. Extending distally from the concave shapedleading surface 18 is a distal tip portion 20, and extending proximallyfrom the concave shaped leading surface 18 is a convex shaped portion22. Both the distal tip portion 20 and the convex shaped portion 22preferably have non-abrasive surfaces. In this configuration, theabrasive grit 19 is effectively prevented from engaging a vessel wallregardless of the orientation of the ablation burr 14 within a vessel.This is shown and described in more detail with reference to FIG. 2.

FIG. 2 shows a vascular lumen 50 having occlusion material 52 and 54disposed therein. To traverse the vascular lumen 50, the guide wire 16may have to assume an “S” shape as shown. This configuration may causethe ablation burr 14 to be oriented at an angle relative to the centralaxis of the vascular lumen 50. When this occurs, the non-abrasivesurfaces of the distal tip 20 and the convex shaped portion 22 will tendto engage the wall of the vessel 50 before the concave shaped leadingsurface 18, and may effectively prevent the abrasive grit 19 fromengaging the vessel wall. Preferably, the convex shaped portion 22 has anumber of dimples 21 formed therein to reduce the friction between theablation burr 14 and the wall of the vessel 50.

It is recognized that the ablation burr 14 may become offset from thecentral axis of a lumen for a number of reasons, and the above exampleis only illustrative. Another illustrative example is when theatherectomy device 10 is substantially less flexible than the guide wire16, which is usually the case. In this situation, and when a relativelysharp bend in the vascular lumen is encountered, the atherectomy devicemay tend to bend the guide wire toward a vessel wall. This may cause theablation burr 14 to improperly engage the vessel wall.

FIG. 3 is a side elevational view of the embodiment shown in FIG. 1ablating an occluded stent. It is recognized that the benefits of theembodiment shown in FIG. 1 may equally apply when the ablation burr isused to remove unwanted deposits (e.g., interstitial hyperplasia) 70from within a stent 72. In this application, however, the presentinvention may effectively prevent the abrasive grit 19 on the concaveshaped leading surface 18 from engaging the stent 72, rather than thevessel wall. This may reduce the risk that the ablating burr 14 willdamage the stent 72. Accordingly, the ablating burr 14 may have an outerdiameter that more closely matches the inner diameter of the stent 72.

Finally, it is contemplated that the material used to form the distaltip 20 and the convex shaped portion 22 may be softer than the materialused to form the stent 72. This may further reduce the chance that theablating burr 14 will damage the stent 72.

FIG. 4 is a side elevational view of an atherectomy device in accordancewith another embodiment of the present invention, including a number offluted depressions in the outer surface of the ablating burr. FIG. 5 isa front view of the embodiment shown in FIG. 4. In this embodiment, theablation burr 100 includes an outer surface 102 which is generallynon-abrasive, and a number of depressions 104 formed therein. Each ofthe number of depressions 104 form a depressed surface. An abrasive isprovided on each of the depressed surfaces as shown, such that theabrasive is located just below the outer surface 102 of the ablationburr 100. In this configuration, only the non-abrasive outer surface 102of the ablation burr 100 contacts the stent, and the occluding materialwithin the stent enters the depressions 104 and becomes ablated.Preferably, the abrasive is a diamond grit, and the number ofdepressions 104 form a number of depressed flutes in the outer surface102 of the ablation burr 100, as shown.

In another embodiment of the present invention, and as shown in FIG. 6,the ablation burr 110 has a generally elliptical outer surface 112 witha selected portion of the outer surface 114 covered with an abrasive.Preferably, the abrasive 114 is applied to either the entire outersurface 112 or to just the leading half of the outer surface 112.

In accordance with the present invention, the abrasive surface 114 isformed from a material that is softer than the material used to form thestent. Thus, the abrasive may not damage the stent if the materialremoval device engages the stent. Preferably, the abrasive comprises anumber of chips or a grit of plastic or some malleable material which issofter than the material used to form the stent. It is known that stentsare typically formed from stainless steel or Nitinol.

In another embodiment, and as shown in FIG. 7, the atherectomy deviceincludes a cutter device 132 rather than an ablation device as describedabove. FIG. 8 is a cross-sectional side view taken along lines 8—8 ofFIG. 7. The cutter device 132 may be generally elliptical in shape asshown, and may have a number of cutter blades 134 on the outer surfacethereof. In accordance with the present invention, at least a portion ofthe cutter blades 134 are made from a material that is softer than thematerial used to form the stent. As indicated above, stents aretypically made from either stainless steel or Nitinol. In the presentembodiment, it is contemplated that selected portions of the cutterblades 134 are made from a softer material such as aluminum (e.g., analuminum alloy 1060-0), pure titanium or annealed stainless steel. Thesematerials are advantageous in that they are very ductile. It iscontemplated, however, that the cutting blades 134 may be hardened byoxidizing, nitriding, carbonizing or by some other process to maintain asharp cutting edge. A sharp cutting edge is often important to minimizethe particle size of the ablated atheroma. If the burr contacts thestent, the underlying ductile burr material preferably plasticallydeforms, thus preventing particle generation from either the burr or thestent.

In the illustrative embodiment, holes 135 connect the outside of theburr (cutting surface) to the inner guide wire lumen 137. The holes 135may be spaced at any angular interval around the diameter of the burrand at multiple points along the length of the burr. For optimumperformance, the holes are preferably angled relative to an axis that isperpendicular to the central axis of the burr, as shown.

The holes 135 preferably perform one or more tasks. For example, theholes 135 may aspirate the ablated material when a vacuum is applied tothe inner guide wire lumen 137. Aspiration of the ablated material mayhelp keep the ablated particulate from being embolized distally of theablation site. Alternatively, the holes 135 may infuse fluid to theablation site. The infusion of fluids may help cool the site (and thushelp prevent restenosis) and/or may help lubricate the ablation site tomake it more difficult to unintentionally cut a vessel wall or ablate astent.

FIG. 9 is a side elevational view of the embodiment shown in FIG. 7cutting through an occluded stent. Because the cutter blades 134 aremade from a material that is softer than the material used to form thestent, the outer diameter of the cutter device 132 may more closelymatch the inner diameter of the stent. This is an advantage of all ofthe above embodiments. That is, in prior atherectomy devices, thematerial removal device typically had an outer diameter that wassubstantially less than the inner diameter of the stent to reduce therisk that the material removal device will engage, and thus damage, thestent. In the present invention, however, appropriate portions of thematerial removal devices (e.g., ablaters or cutters) may be formed froma softer material than the stent, which may protect the stent. Inaddition, the abrasive surfaces may be designed to not engage the stent.Accordingly, the material removal device may have an outer diameter thatmore closely matches the inner diameter of the stent, which may allowthe material removal device to remove more of the occluding matter fromwithin the stent.

Referring now to FIG. 10, an atherectomy device 150 is illustrated,having an atherectomy burr 152 for removing unwanted material. Burr 152includes a proximal shoulder 156, a distal shoulder 158, and is securedto the distal end of flexible drive shaft 12. Drive shaft 12 and burr152 have a lumen therethrough, allowing passage of guide wire 16. Anintermediate material removal portion 160 lies between proximal shoulder156 and distal shoulder 158. In the preferred embodiment, illustrated inFIG. 10, material removal portion 160 is abrasive. One embodimentcontains abrasive grit secured to the burr outer surface. Anotherembodiment includes abrasive chips fixed to the outer surface. Apreferred abrasive material includes diamonds. Yet another embodimentincludes cutting blades in the material removal portion.

In the embodiment illustrated, abrasive portion 160 is recessed relativeto the proximal and distal shoulders, having a smaller radial extent andcircumference than the maximum radial extent of either of the shoulders.In a preferred embodiment, transition portions lie between abrasiveportion 160 and the distal and proximal shoulders. In the embodimentillustrated, a proximal transition portion 164 and a distal transitionportion 162 lie between abrasive portion 160, and proximal shoulder 156and distal shoulder 158, respectively. In one embodiment the transitionportions have a straight taper while in another embodiment thetransition portions have a rounded taper. In yet another embodiment, thetransition portions are substantially larger, and can approach the sizeof the shoulders. In this embodiment, the larger transition portionsimpart a dumbbell appearance to the atherectomy burr.

Referring now to FIG. 11, atherectomy device 150 is illustrated disposedwithin vessel 50 between a first deposit 52 and a second deposit 54.Deposits 52 and 54 are deposited on opposite sides of vessel 50,creating a tortuous path through the vessel. The path illustrated forcesatherectomy burr 152 to can't relative to the vessel longitudinal axis,forcing distal shoulder 158 into contact with the wall of vessel 50 asindicated at 166. If distal shoulder region 166 was abrasive, therotating, abrasive portion could be forced into contact with the vesselwall. If drive shaft 16 is pushed in a distal direction with sufficientforce, it is also possible in some vessel geometries, to force proximalshoulder 156 into an opposite wall of the vessel as well.

As indicated at 170, abrasive portion 160 is brought to bear againstdeposit 52, allowing the unwanted material to be removed by the rotatingatherectomy burr. At the same time, less abrasive distal shoulder 166 ispresented to the wall of vessel 50. As burr 152 is advanced over guidewire 16, distal shoulder 166 will follow a path between the vessel walland the deposit, and will present abrasive portion 160 to the deposit inregion 168. At this location, distal shoulder 166 can act to align burr152 with the path or channel between the deposit and the vessel wall. Aninwardly projecting portion of deposit 52 will be presented to recessed,abrasive portion 160, while the smooth vessel wall will notsubstantially protrude into the recessed, abrasive portion. The depositcan be removed while the vessel wall remains untouched by the abrasive.

The cam action of the burr shoulders thus acts to align the abrasive orcutting action of the burr with the path through the vessel anddeposits. The improved burr can reduce the wear on a vessel wallassociated with cutting the corner of a bifurcated ostial lesion.

A currently preferred embodiment of the atherectomy device according tothe present invention is illustrated in FIG. 12. The atherectomy device210 includes an ablation burr 214 having a generally concave front orleading surface 219 and a generally ellipsoidal rear or trailing surface233. The concave front surface is positioned between an inner,relatively smooth, circumferential rim 215 at the distal tip of the burrand an outer relatively smooth circumferential rim 216 that ispositioned proximal to the inner circumferential rim 215. The diameterof the inner circumferential rim is preferably just larger than thediameter of a cylindrical lumen that extends through the burr forpassage of a guide wire. The diameter of the outer circumferential rim216 is preferably equal to the maximum diameter of the burr. The leadingsurface 219 of the burr is concave in cross section and is covered withan abrasive material 220, for example, diamond grit, to ablate anobstruction as the burr is rotated. Similar to the embodiments discussedpreviously, the burr is coupled to a drive shaft 221 that selectivelyrotates the burr at high speed.

The inner and outer circumferential rims 215, 216 are concentric, andare spaced longitudinally by a distance 217. The distance 217 isselected to adjust the pitch or “flatness” of the leading surface.

In a currently preferred embodiment of the ablation burr, as illustratedin FIG. 13, the outer circumferential rim 216 includes a convex topsurface 222. In a preferred embodiment, the outer circumferential rimhas a width 223 of approximately 0.001-0.004 inches, and is preferably0.002 inches wide.

It is believed that potential trauma to the artery or stent, and anypotentially resulting complications, are minimized by providing anablation device having the configuration illustrated in FIG. 12, giventhe smooth convex outer circumferential rim 216 and the shape andreduced surface area of the first leading surface 219. In particular, ifthe burr contacts the vessel wall, the area of contact between theabrasive and the vessel wall is reduced. It is further believed thatgiven the proximity of the abrasive to a longitudinal axis of the burr,the speed of the movement of a majority of the abrasive surface isreduced for a given RPM. As a result, an ablation device provided inaccordance with this presently preferred embodiment of the inventionablates a desirably sized lumen, while reducing hemolysis and plateletaggregation.

It is further believed that an ablation device provided in accordancewith this embodiment of the present invention reduces RPM dropinconsistency. When in use, the burr is spun at approximately 180,000RPM. When the burr engages the lesion or unwanted deposits, the ablationprocess causes a drop of approximately 5,000 RPM. As will be understoodby one of ordinary skill in the art, it is desirable to maintain aconsistent RPM drop of 5,000 during ablation of the lesion. If anexcessive RPM drop occurs, it is typically accompanied by increasedtorque and an undesirable increase in heat, as well as an increase inthe quantity and size of particles generated by the ablation. It isbelieved that a more stable drop in RPM is achieved by reducing theabrasive surface area in contact with the lesion, and providing asteeper angle of contact with the lesion. As illustrated in FIGS. 14 and15, the leading surface 219 is provided with a selected curvature suchthat the leading surface extends away from the outer circumferential rim216 towards the inner circumferential rim 215 at a desired contact angle224 measured relative to the outer circumferential rim 216. The steeperthe contact angle, the less likely it is that the abrasive outer surfacewill contact the wall of the vessel or stent. It is also less likelythat the abrasive will contact a vessel wall, when the burr ismaneuvered around a corner. It is further believed that a steeper angleof contact and reduced abrasive surface area lessens the impact of sideforces and potential vibrations that can result from fluctuations in theaxial load applied by the operator.

In an alternative embodiment, illustrated in FIG. 16, a guide wire 225extends co-axially through the burr. A distal end 226 of the wireextends out of the burr, distal to the inner circumferential rim 215. Anabrasive tip 227 is coupled to the distal end of the wire. The wire maybe keyed or coupled to the burr such that the wire and burr spinsimultaneously, as illustrated in FIG. 16. Alternatively, as illustratedin FIG. 17, the guide wire 225 may be coupled to a motor (not shown) ata proximal end, which spins the wire independently of the burr. Asfurther illustrated in FIG. 17, the burr 214 is coupled to a sheath 249which in turn extends through an outer catheter sheath 250. The abrasivetip is made of a highly radiopaque material, allowing the device to bemaneuvered using fluoroscopy, as is known in the art. In a preferredembodiment, the wire is spun at a rate of between 10,000-100,000 RPM. Anablation device provided in accordance with this embodiment may beparticularly useful where the obstruction is extensive, making itdifficult to pass a conventional guide wire through the obstruction. Thetip 227 of the wire ablates the obstruction, helping to create a pathfor the burr. This embodiment provides the added benefit of working awire across the lesion, such that if the vessel spasms and collapses, apath is available to facilitate the reopening of the vessel.

In yet another embodiment of the ablation device illustrated in FIGS. 18and 19, the burr 214 is made of a compressible, elastomeric material.The burr is positioned in a compressed condition 228 having a firstdiameter 252 within a guide catheter 229. Once the guide catheter ismaneuvered through a patient's vasculature to a desired location, theburr is pushed out of the catheter, allowing the burr to expand to asecond expanded condition 230 having a second diameter 253, as seen inFIG. 19. While a variety of materials may be used, the burr body may bemade of a polymeric material such as urethane, or foam, or it may behollow by providing a skin that is supported by one or more expandableribs.

To facilitate the deployment of the burr from the catheter, a lubricantsuch as Bio-Slide is placed on at least a portion of the ellipsoidaltrailing surface 233 that extends proximally from the second annularedge 216 to the drive shaft 221. In this manner, it is possible toreduce the width of the burr to facilitate placement, particularly whenit is necessary to pass through narrow openings, such as the coronaryostia. For example, a catheter used to position the ablation device inthe coronary ostia typically cannot exceed 8 French. When usingconventional burrs, this would therefore limit the maximum diameter ofthe burr and resulting lumen to approximately 2 mm. However, byproviding a burr in accordance with the present invention, the burr hasa maximum diameter of 2 mm when positioned in the first compressedcondition within the catheter, and expands to a diameter of 3 mm whendeployed from the catheter. As a result, it is possible to create a 3 mmwide lumen in a single pass in a region where it was previously onlypossible to create a 2 mm lumen in a single pass.

In order to couple the polymeric material that comprises the body of theburr to the drive shaft, a pin 231 having a plurality of radiallyextending splines 232 is provided, as illustrated in FIG. 20. Theelastomeric burr is cast over the splines, such that the splinesmechanically grasp the elastomeric material. The pin 231 is coupled tothe drive shaft, thereby coupling the elastomeric burr to the shaft.

Although the drive shaft 221 may be made of a variety of materials, in apreferred embodiment, as illustrated in FIG. 21, the shaft is comprisedof an inner coil 234, and outer coil 236, and a middle layer 234provided between the inner and outer coils. In a preferred embodiment,the inner coil 234 is formed of a wire or strip wound in a first lay,the outer coil 236 is formed of a wire or strip wound in a second layopposite that of the first lay, and the middle layer 235 is formed of alongitudinally rigid material. In a preferred embodiment, the middlelayer is formed of a number of straight wires or strips, orientedparallel to a longitudinal axis 237 of the drive coil. Alternatively,the middle layer may be formed of heat shrink, thin walled hypotube,polymer tubing, or any other longitudinally rigid material. As a result,the drive shaft 221 maintains high bending flexibility while increasingits longitudinal stiffness.

In a preferred embodiment, an ablation device 246 is advanced to adesired site within a patient's vasculature over a guide wire 238. Asillustrated in FIGS. 22 and 23, a bearing 239 is coupled to a distalregion 240 of the guide wire. As best seen in FIG. 23, the bearing 239has a static member 242 coupled to the guide wire which does not move,and a dynamic member 241 that is free to rotate over the guide wire andis separated from the static member by ball bearings 243. The dynamicmember 241 acts as a bumper and rotates when the ablation device isadvanced to the distal region of the guide wire and contacts the dynamicmember 241. In a preferred embodiment, the guide wire 238 having abearing 239 is advanced through the patient's vasculature 212 until thebearing 239 is positioned just distal of the unwanted deposit or lesion211. Conventionally, when the ablation device works through the distalend of a lesion, the sudden lack of resistance results in the ablationdevice darting forward and engaging the spring tip 251 that is securedto the distal end of the guide wire. The friction caused by the rotatingburr may generate sufficient heat to weld the burr to the spring tip 251of the guide wire. By positioning a bearing 239 on the guide wire, andpositioning the guide wire such that the bearing is located just distalof the lesion, darting and the associated problems are substantiallyeliminated. In a preferred embodiment, an outer surface 244 of thedynamic member 241 has a low durometer, to prevent the dynamic memberfrom ablating the inner wall of the vessel or stent as it rotates.

FIG. 24 illustrates an atherectomy device according to yet anotheraspect of the present invention. The atherectomy device 300 includes anablation burr 302 having a generally concave leading surface 304. Anabrasive covers a portion of the leading surface in order to ablate anocclusion within a patient's blood vessel in the manner described above.The leading surface 304 includes one or more ports 306 through whichaspirated particles 308 may be removed from the patient's blood vessel.

The burr 302 includes a proximal, central lumen 310 into which a sealeddrive shaft 312 is fitted. A distal central lumen is provided for thepassage of a guide wire. The drive shaft 312 generally comprises alength of heat shrink tubing or other non-permeable material sandwichedbetween two windings. The drive shaft 312 has a central lumen that is influid communication with the aspiration ports 306 on the leading surfaceof the burr. The proximal end of the sealed drive shaft 312 is connectedto a coupler 314. A central portion 316 of the coupler 314 includes awindow 318 through which fluid may be drawn. A conventional drive shaft320 is secured at the proximal end of the coupler 314. A sheath 321surrounds the driveshaft 320 such that a lubricating fluid can beinjected between the sheath 321 and the driveshaft 320.

Surrounding the sheath 321 and coupler 314 is an outer sheath 322. Theproximal end of the sheath 322 is connected to a vacuum source and acollection jar in series with the vacuum source. Particles removed fromthe patient's vessel therefore travel through the aspiration ports 306on the leading surface of the burr, through the sealed drive shaft 312,out the window 318 and along a passage 319 contained between the innerdiameter of the outer sheath 322 and the outer diameter of the sheath321. The gap between the sheath 321 and the outer sheath 322 is sealedproximal to the point at which the outer sheath is coupled to the sourceof vacuum.

The placement of the aspiration ports 306 prevents their direct contactwith healthy tissue. This feature coupled with the highly flexiblesealed drive shaft may allow the device to be used in treating suchdiseases as Saphenous Vein Graft disease or other diseased havinglesions with thrombus.

From the foregoing, it will be appreciated that although embodiments ofthe invention have been described herein for purposes of illustration,various modifications may be made without deviating from the spirit ofthe invention. It will also be understood that it is possible to use thevarious embodiments described herein in various combinations with eachother. Thus, the present invention is not limited to the embodimentdescribed herein, but rather is defined by the claims which follow.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. An atherectomy devicecomprising: a solid burr body having: a distal end and proximal end anda concave leading surface with a radius about a longitudinal axis of theburr body that increases from the distal end of the burr to a point thatis proximal to the distal end; an abrasive on the concave leadingsurface; and one or more aspiration ports disposed on the concaveleading surface of the burr; a substantially sealed drive shaft coupledto the burr, the scaled drive shaft including a lumen that is in fluidcommunication with the one or more aspiration ports on the leadingsurface of the burr, and a source of vacuum coupled to the sealed driveshaft to withdraw particles ablated from a patient's vessel as the burris rotated.
 2. The atherectomy device of claim 1, further comprising: acoupler into which the sealed drive shaft is fitted, a second driveshaft received in the coupler, a sleeve fitted over the second driveshaft and coupler, the coupler including a window through whichparticles drawn through one or more aspiration ports are passed.
 3. Theatherectomy device of claim 1, wherein the radius of the concave leadingsurface lies entirely below an imaginary line that extends between thedistal end and the point proximal to the distal end.